DTV transmitter and method of processing digital broadcast data therein

ABSTRACT

A DTV transmitter includes a signal generator, an interleaver, a trellis encoder, and a modulator. The signal generator generates a first data group including first, second and third regions, the first and third regions including main data and RS parity data, the second region including enhanced data coded with a first coding rate, enhanced data coded with a second coding rate, a plurality of known data sequences, signaling information and RS parity data. The interleaver interleaves the first data group to generate a second data group including fourth, fifth and sixth regions, the fifth region including enhanced data, a plurality of known data sequences, signaling information, and RS parity data, the fourth region including main data, RS parity data, and enhanced data. The trellis encoder trellis-encodes the second data group. The modulator modulates a broadcast signal including the trellis encoded second data group.

This application claims the benefit of the Korean Patent Application No.10-2006-0063877, filed on Jul. 7, 2006, which is hereby incorporated byreference as if fully set forth herein. Also, this application claimsthe benefit of the Korean Patent Application No. 10-2006-0089736, filedon Sep. 15, 2006, which is hereby incorporated by reference as if fullyset forth herein. This application also claims the benefit of U.S.Provisional Application No. 60/884,203, filed on Jan. 9, 2007, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to digital television (DTV) systems andmethods of processing DTV signals.

2. Discussion of the Related Art

Presently, the technology for processing digital signals is beingdeveloped at a vast rate, and, as a larger number of the population usesthe Internet, digital electric appliances, computers, and the Internetare being integrated. Therefore, in order to meet with the variousrequirements of the users, a system that can transmit diversesupplemental information in addition to video/audio data through adigital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the video/audio data. However, withthe advent of digital broadcasting, digital television receiving systemsthat receive only video/audio data are already supplied to the market.Therefore, the supplemental data that are transmitted through the samechannel as the video/audio data should not influence the conventionalreceiving systems that are provided in the market. In other words, thismay be defined as the compatibility of broadcast system, and thesupplemental data broadcast system should be compatible with thebroadcast system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional receiving system may bedeteriorated. More specifically, resistance to changes in channels andnoise is more highly required when using portable and/or mobilereceivers.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to DTV systems andmethods of processing signals that substantially obviate one or moreproblems due to limitations and disadvantages of the related art.

An object of the present invention is to provide DTV systems and methodsof processing signals that are highly resistant to channel changes andnoise.

Another object of the present invention is to provide DTV systems andmethods of processing signals that can also enhance the receivingperformance of a digital broadcast receiving system by using pre-definedknown data already known by the receiving system and the transmittingsystem in demodulation and channel equalization processes.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) receiving system includes an informationdetector, a timing recovery unit, a carrier recovery unit, and a phasecompensation unit. The information detector detects position informationof a known data sequence which is periodically repeated in a digitaltelevision (DTV) signal and estimates an initial frequency offset valuefrom the DTV signal. The timing recovery unit performs timing recoveryon the DTV signal by detecting timing error information from the DTVsignal using the position information of the known data sequence. Thecarrier recovery unit performs carrier recovery on the DTV signal byestimating a frequency offset value of the DTV signal using the positioninformation of the known data sequence. The phase compensation unitcompensates a phase offset of the DTV signal using the positioninformation of the known data sequence.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram of a digital broadcast transmittingsystem according to an embodiment of the present invention;

FIG. 2 illustrates a structure of a data group according to anembodiment of the present invention;

FIG. 3 illustrates an example of known data having identical patternsbeing periodically inserted according to the present invention;

FIG. 4 illustrates a block diagram of a demodulating unit of a digitalbroadcast receiving system according to an embodiment of the presentinvention;

FIG. 5 illustrates a block diagram of a demodulator shown in FIG. 4;

FIG. 6 illustrates a block diagram of a known data detector and initialfrequency offset estimator shown in FIG. 4;

FIG. 7 illustrates a block diagram of a DC remover shown in FIG. 4;

FIG. 8 illustrates an example of relocating sample data inputted to a DCestimator shown in FIG. 7;

FIG. 9 illustrates a block diagram of a digital broadcast transmittingsystem according to another embodiment of the present invention;

FIG. 10 and FIG. 11 illustrate another examples of data configuration atbefore and after ends of a data deinterleaver in a transmitting systemaccording to the present invention;

FIG. 12 illustrates a block diagram of a demodulating unit of a digitalbroadcast receiving system according to another embodiment of thepresent invention;

FIG. 13 illustrates a block diagram of a digital broadcast receivingsystem according to an embodiment of the present invention; and

FIG. 14 illustrates a block diagram of a digital broadcast receivingsystem according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather forecast, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitting system and thereceiving system. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data. More specifically, in a digital broadcasttransmitting system for multiplexing main data with enhanced data havinginformation included therein known data having a pattern formed inaccordance with a pre-arrangement between the receiving system and thetransmitting system may also be multiplexed and transmitted in order toenhance the receiving performance. The present invention relates toenhancing the receiving performance of the receiving system by detectingknown data transmitted from the transmitting system and using thedetected known data in the demodulation process.

FIG. 1 illustrates an example of a digital broadcast transmitting systemaccording to the present invention for transmitting known data. Thedigital broadcast transmitting system of FIG. 1 is merely an exampleproposed to facilitate the understanding of the present invention.Herein, any transmitting system that can transmit known data sequencesmay be adopted in the present invention. Therefore, the presentinvention is not limited to the example proposed in the description setforth herein.

The digital broadcast transmitting system of FIG. 1 includes apre-processor 101, a packet formatter 102, a packet multiplexer 103, adata randomizer 104, a RS encoder/non-systematic RS encoder 121, a datainterleaver 122, a parity replacer 123, a non-systematic RS encoder 124,a trellis-encoding module 125, a frame multiplexer 126, and atransmitting unit 130. In the digital broadcast transmitting systemhaving the above-described structure, the pre-processor 101 receives andpre-processes the enhanced data by performing pre-processes, such asadditional block encoding, block interleaving, and byte-expansion byinserting null data. Then, the pre-processed enhanced data are outputtedto the packet formatter 102.

At this point, when the inputted enhanced data correspond to differenttypes of enhanced data, for example, when the inputted enhanced datacorrespond to high priority data and low priority data, thepre-processor 101 individually performs pre-processes such as additionalblock encoding, block interleaving, and byte-expansion. Thereafter, theenhanced data, which are identified in accordance with the importance(or priority) of the corresponding data, maintain the identified stateand are then outputted to the packet formatter 102. Furthermore,pre-processes, such as additional block encoding, block interleaving,and byte-expansion, may also be identically performed on all enhanceddata, thereby being outputted to the packet formatter 102.

Based upon the control of the scheduler 105, the packet formatter 102adds a 4-byte MPEG header to the pre-processed enhanced data, therebyconfiguring a 188-byte enhanced data packet. At this point, the enhanceddata packet may be configured of enhanced data only, or configured ofknown data (or known data place holder) only, or configured of enhanceddata multiplexed with known data. The output of the packet formatter 102is inputted to the packet multiplexer 103. Based on the control of thescheduler 105, the packet multiplexer 103 multiplexes the main datapacket and the enhanced data packet in packet units and outputs themultiplexed packet to the data randomizer 104.

The scheduler 105 controls the packet formatter 102 and the packetmultiplexer 103 so that the interleaved data are formed into a datagroup divided into a plurality of hierarchical areas in a later process.The scheduler 105 also controls the insertion of the MPEG header andknown data (or known data place holders) into the enhanced data packet.More specifically, the scheduler 105 also controls the insertionposition of the known data (or known data place holders) so as to enablethe known data sequences periodically inserted in the transmission dataframe from the receiving system to be received. Furthermore, whenrequired, the scheduler 105 may also control the insertion position ofthe known data (or known data place holders) so as to enable the knowndata sequences non-periodically inserted in the transmission data framefrom the receiving system to be received.

FIG. 2 illustrates an example of a data frame structure configured basedupon the control of the scheduler 105. Most particularly, FIG. 2illustrates an example of dividing the data groups into head, body, andtail areas based upon the output of the data interleaver in a laterprocess. Referring to FIG. 2, the head, body, and tail areas are eachdivided in 52-packet units. However, this is merely exemplary. Thenumber of packets included in the head, body, and tail areas may bealtered and varied by the system designer. Therefore, the presentinvention will not be limited to the above-described example.

In addition, with respect to the output of the data interleaver, thebody area is allocated to include at least a portion or the entire areain which enhanced data are consecutively outputted. In the body area,the known data are periodically inserted at a constant rate. The headarea is located before the body area, and the tail area is located afterthe body area. For example, referring to FIG. 2, the main data are notincluded in the body area, and the known data are inserted after each6-packet (or segment) cycle. Furthermore, the known data areadditionally inserted at the beginning of the body area. In this case,the body area may show a stronger receiving performance, since there isno interference from the main data. The enhanced data of the head andtail areas are mixed with the main data in accordance with the outputorder from the interleaver. Accordingly, the receiving performance inthe head and tail areas is more deteriorated than in the body area.

The output data of the packet multiplexer 103 are inputted to the datarandomizer 104. The data randomizer 104 discards (or deletes) the MPEGsynchronization byte and randomizes the remaining 187 bytes by using apseudo-random byte, which is generated from inside the data randomizer104. Thereafter, the randomized data are outputted to a post-processor110. Herein, the post-processor 110 includes a Reed-Solomon (RS)encoder/non-systematic RS parity place holder inserter 111, a datainterleaver 112, a block processor 113, a data deinterleaver 114, and aRS byte remover 115. The RS encoder/non-systematic RS parity placeholder inserter 111 of the post-processor 110 processes the randomizeddata with a systematic RS-coding process, when the randomized datacorrespond to the main data packet. Alternatively, the RSencoder/non-systematic RS parity place holder inserter 111 processes therandomized data with a non-systematic RS parity place holder insertionprocess, when the randomized data correspond to the enhanced datapacket. More specifically, if the randomized 187-byte data packetcorresponds to the main data packet, the randomized 187-byte data packetbeing outputted from the data randomizer 104, a systematic RS encodingprocess is performed as in the conventional system so as to add a20-byte parity at the end of the 187-byte data. Then, the processed dataare outputted to the data interleaver 112. On the other hand, if therandomized 187-byte data packet corresponds to the enhanced data packet,the randomized 187-byte data packet being outputted from the datarandomizer 104, in order to perform the non-systematic RS encodingprocess, a non-systematic RS parity place holder configured of 20 nulldata byte is inserted in the randomized data packet. Also, data byteswithin the enhanced data packet are inserted in each place of theremaining 187 data bytes. Thereafter, the processed data are outputtedto the data interleaver 112.

The data interleaver 112 performs a data interleaving process on theoutput of the RS encoder/non-systematic RS parity place holder inserter111 and, then, outputs the interleaved data to the block processor 113.The block processor 113 performs additional encoding in block units onlyon the enhanced data that are outputted from the data interleaver 112and outputs the additionally encoded enhanced data to the datadeinterleaver 114. The data deinterleaver 114 performs an inverseprocess of the data interleaver 112 by deinterleaving the inputted dataand outputs the deinterleaved data to the RS byte remover 115.

The RS byte remover 115 removes the 20-byte parity data, which wereinserted by the RS encoder/non-systematic RS parity place holderinserter 111. If the inputted data correspond to the main data packet,the last 20 bytes are removed from the total 207 data bytes. And, if theinputted data correspond to the enhanced data packet, the 20 bytes ofthe parity place holders that were inserted to perform thenon-systematic RS-encoding process are removed from the total 207 databytes. This is to recalculate the parity, since the initial data havebeen modified by the block processor 113 in case of the enhanced data.The output of the RS byte remover 115 is then inputted to the RSencoder/non-systematic RS encoder 121.

The RS encoder/non-systematic RS encoder 121 adds 20-byte parity data tothe 187-byte packet outputted from the RS byte remover 115. Then, theprocessed data packet is outputted to the data interleaver 122. At thispoint, if the inputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 121 performs a systematic RS-encodingprocess identical to that of the conventional broadcasting system,thereby adding 20 bytes of parity at the end of the 187-byte unit data.Alternatively, if the inputted data correspond to the enhanced datapacket, the RS encoder/non-systematic RS encoder 121 decides 20 paritybyte places within the data packet. Then, the RS encoder/non-systematicRS encoder 121 performs a non-systematic RS-encoding process in each ofthe decided parity byte places within the enhanced data packet, therebyinserting the 20-byte RS parity. Herein, the data interleaver 122corresponds to a byte unit convolutional interleaver. The sameinterleaving rule of the data interleaver 112 is also applied to thedata interleaver 122. The output of the data interleaver 122 is inputtedto the parity replacer 123 and the non-systematic RS encoder 124.

Meanwhile, a process of initializing a memory within the trellisencoding module 125 is primarily required in order to decide the outputdata of the trellis-encoding module 125, which is located after theparity replacer 123, as the known data defined by the receiving systemand the transmitting system. At this point, in order to performinitialization, initialization data is required to be generated and toreplace the input data of the trellis encoding module 125 so as toperform initialization in accordance with the memory status.Accordingly, the RS parity that is influenced by the replacedinitialization data is required to be recalculated in order to replacethe RS parity being outputted from the data interleaver 122. Therefore,the non-systematic RS encoder 124 receives a pre-calculatednon-systematic RS parity with respect to the enhanced data packet, whichincludes data that are to be replaced with the initialization data ofthe memory, from the data interleaver 122. The non-systematic RS encoder124 also receives initialization data from the trellis encoding module125. Thereafter, a new non-systematic RS parity is calculated and thenoutputted to the parity replacer 123.

If the main data packet is inputted, or if the enhanced data packet,which does not include any initialization data that are to be replaced,is inputted, the parity replacer 123 selects the RS parity and data thatare outputted from the data interleaver 122, which are then outputted tothe trellis encoding module 125. Meanwhile, if the enhanced data packetincluding initialization data that are to be replaced is inputted, theparity replacer 123 selects the output of the data interleaver 122 forthe data and selects the output of the non-systematic RS encoder 124 forthe RS parity, which are then outputted to the trellis encoding module125.

The trellis encoding module 125 converts the byte-unit data to symbolunits and performs a 12-way interleaving process so as to trellis-encodethe received data. Thereafter, the processed data are outputted to theframe multiplexer 126. The frame multiplexer 126 inserts a fieldsynchronization signal and a segment synchronization signal to the dataoutputted from the trellis encoding module 125 and, then, outputs theprocessed data to the transmitting unit 130. Herein, the transmittingunit 130 includes a pilot inserter 131, a modulator 132, and a radiofrequency (RF) up-converter 133. The operations and roles of thetransmitting unit 130 and its components are identical to those of theconventional transmitter. Therefore, detailed description of the samewill be omitted for simplicity.

In transmitting known data, the above-described digital broadcasttransmitting system may non-periodically insert known data within atransmission data frame and transmit the processed data. Alternatively,the digital broadcast transmitting system may periodically insert knowndata within a transmission data frame and transmit the processed data,as shown in FIG. 3. At this point, it is assumed that the known datasequences that are repeated in accordance with a constant cycle periodhave the same pattern. More specifically, known data sequences havingthe same pattern may be periodically inserted in the enhanced datapacket (or group) and then transmitted. Alternatively, known datasequences having different patterns may be periodically ornon-periodically inserted in the enhanced data packet (or group) andthen transmitted. Such information may be pre-known by the receivingsystem or may be transmitted from the transmitting system along with theknown data sequence.

FIG. 3 illustrates an example of configuring and transmitting a datastructure so that A number of known data symbols are repeated at Bnumber of symbol cycle periods. Referring to FIG. 3, the data indicatedas (B-A) symbols may correspond to the enhanced data or to the main dataor to a combination of the enhanced data and the main data. In thedescription of the present invention, the above-described data will behereinafter referred to as valid data so as to be distinguished from theknown data. When known data having the dame pattern are periodicallyinserted as described above, the receiving system uses the known data asa training sequence, thereby enhancing the receiving performance. Forexample, the equalizer of the receiving unit may use the above-describedknown data so as to obtain an accurate decision value. The equalizer mayalso use the known data in order to estimate a channel impulse response.Furthermore, the demodulating unit within the receiving unit may use thecorrelation between the known data and the received signal so as toperform carrier recovery and timing clock recovery processes withstability.

FIG. 4 illustrates an example of a demodulating unit of the digitalbroadcast receiving system according to the present invention. Referringto FIG. 4, the digital broadcast receiving system includes ananalog/digital converter (ADC) 410, a demodulator 420, a known datadetector and initial frequency offset estimator 430, an equalizer 440,and an error correction unit 450. Herein, the error correction unit 450includes a block decoder 451, a data deinterleaver 452, a RSdecoder/non-systematic RS parity remover 453, a derandomizer 454, a maindata packet remover 455, a packet deformatter 456, and an enhanced dataprocessor 457. More specifically, a signal of a particular channel tunedby a tuner is inputted to the A/D converter 410 in the form of an analogsignal. The A/D converter 410 digitalizes the analog signal of theparticular channel and outputs the digitalized signal to the demodulator420. The demodulator 420 performs carrier recovery and timing recoveryprocesses on digitalized pass band signals, so as to change thedigitalized pass band signals to baseband signals. Thereafter, thebaseband signals are outputted to the known data detector and initialfrequency offset estimator 430 and the equalizer 440.

The known data detector and initial frequency offset estimator 430estimates known data place information (or a known sequence positionindicator), known data sequences corresponding to the place information,and an initial frequency offset, which have been inserted by thetransmitting system, from the input/output data of the demodulator 420(i.e., the data prior to demodulation or the data after demodulation).Thereafter, the estimated data are outputted to the demodulator 420 andthe equalizer 440. Accordingly, the demodulator 420 uses the known datasymbol sequence during the timing and/or carrier recovery, therebyenhancing the demodulating performance. Similarly, the channel equalizer440 uses the known data, thereby enhancing the equalizing performance.Detailed description of the timing recovery and carrier recovery of thedemodulator 420 using the known data will be given in a later process.

Furthermore, the equalizer 440 compensates the distortion included inthe demodulated signal and occurring within the channel. Then, thecompensated data are outputted to the block decoder 451 of the errorcorrection unit 450. At this point, the equalizer 440 uses the knowndata information to enhance the equalization performance. Furthermore,the equalizer 440 may use an 8-level decision value decided from theblock decoder 451, thereby enhancing the equalization performance.

Meanwhile, the data that are inputted to the block decoder 451 from theequalizer 440 correspond to the main data that are only processed withtrellis encoding by the trellis encoding module and not processed withadditional encoding by the block processor of the transmitting system,or to the known data, or to the enhanced data that are processed withboth additional encoding and trellis-encoding by the transmittingsystem, the block decoder 604 performs trellis decoding and additionaldecoding processes as inverse processes of the transmitting system. Ifthe data that are inputted to the block decoder 451 correspond to themain data or the known data, the block decoder 451 may either performViterbi decoding on the inputted data or may hard decide a correspondingsoft decision value and output the hard-decided result. Furthermore,since the transmitting system considers the RS parity byte and the MPEGheader byte, both added to the enhanced data packet from thetransmitting system, as the main data, additional encoding is notprocessed on the RS parity byte and MPEG header byte. Similarly, theblock decoder 451 may either perform Viterbi decoding on the RS paritybyte and MPEG header byte or may hard decide a corresponding softdecision value and output the hard-decided result.

Alternatively, if the inputted data correspond to the enhanced data, theblock decoder 451 may output either a hard decision value or a softdecision value on the inputted enhanced data. If the block decoder 451outputs the soft decision value, the performance of an additional errorcorrection decoding process, which is performed on the enhanced data bythe enhanced data processor 457 in a later process, may be enhanced.Hereinafter, an example of the block decoder 451 outputting a softdecision value with respect to the enhanced data will now be described.

The output of the block decoder 451 is inputted to the datadeinterleaver 452. The data deinterleaver 452 performs an inverseprocess of the data interleaver included in the transmitting system andoutputs the deinterleaved data to the RS decoder/non-systematic RSparity remover 453. When the inputted data packet corresponds to a maindata packet, the RS decoder/non-systematic RS parity remover 453performs a systematic RS decoding process. Alternatively, when theinputted data packet corresponds to an enhanced data packet, the RSdecoder/non-systematic RS parity remover 453 removes the non-systematicRS parity byte that has been inputted to the data packet in an earlierprocess. Thereafter, the RS decoder/non-systematic RS parity remover 453outputs the processed data to the derandomizer 454.

The derandomizer 454 receives the data outputted from the RSdecoder/non-systematic RS parity remover 453 and generates a pseudorandom data byte identical to that of the randomizer included in thedigital broadcast transmitting system (or DTV transmitter). Thereafter,the derandomizer 454 performs a bitwise exclusive OR (XOR) operationbetween the generated pseudo random data byte and the data packetoutputted from the RS decoder/non-systematic RS parity remover 453,thereby inserting the MPEG synchronization bytes to the beginning ofeach packet so as to output the data in 188-byte data packet units. Theoutput of the derandomizer 454 is inputted to a main MPEG decoder (notshown) and to the main data packet remover 455 at the same time. Themain MPEG decoder performs decoding only on the data packetcorresponding to the main MPEG. Herein, since the enhanced data packetincludes a null PID or a reserved PID, which is not used by theconventional receiving system, the enhanced data packet is not used bythe main MPEG decoder for decoding and, therefore, disregarded.

However, it is difficult to perform a bitwise exclusive OR (XOR)operation between the soft decision value of the enhanced data and thepseudo random bit. Therefore, as described above, depending upon thecode of the soft decision value, a hard decision is performed on thedata that are to be outputted to the main MPEG decoder. Then, an XORoperation is performed between the pseudo random bit and the harddecided data, which are then outputted. More specifically, if the codeof the soft decision value is a positive number, the hard decision valueis equal to ‘1’. And, if the code of the soft decision value is anegative number, the hard decision value is equal to ‘0’. Thereafter, anXOR operation is performed between the pseudo random bit and any one ofthe hard decided values.

As described above, a soft decision is required in the enhanced dataprocessor 457 in order to enhance the performance when decoding theerror correction code. Therefore, the derandomizer 454 creates aseparate output data with respect to the enhanced data, which is thenoutputted to the main data packet remover 455. For example, when thepseudo random bit is equal to ‘1’, the derandomizer 454 changes the codeof the soft decision value and then outputs the changed code. On theother hand, if the pseudo random bit is equal to ‘0’, the derandomizer454 outputs the soft decision value without any change in the code.

As described above, if the pseudo random bit is equal to ‘1’, the codeof the soft decision value is changed because, when an XOR operation isperformed between the pseudo random bit and the input data in therandomizer of the transmitting system, and when the pseudo random bit isequal to ‘1’, the code of the output data bit becomes the opposite ofthe input data (i.e., 0 XOR 1=1 and 1 XOR 0=0). More specifically, ifthe pseudo random bit generated from the derandomizer 454 is equal to‘1’, and when an XOR operation is performed on the hard decision valueof the enhanced data bit, the XOR-operated value becomes the oppositevalue of the hard decision value. Therefore, when the soft decisionvalue is outputted, a code opposite to that of the soft decision valueis outputted.

The main data packet remover 455 acquires only the soft decision valueof the enhanced data from the output of the derandomizer 454. Then, themain data packet remover 455 outputs the acquired soft decision value.More specifically, the main data packet remover 455 removes the 188 byteunit main data packet from the output of the derandomizer 454 andacquires only the soft decision value of the enhanced data packet,thereby outputting the processed data packet to the packet deformatter456. The packet deformatter 456 first removes the MPEG header so as toobtain a 184-byte unit data packet. Herein, the MPEG header includes aPID for the enhanced data, which was inserted from the transmittingsystem in order to distinguish the enhanced data from the main datapacket in an earlier process. Thereafter, the 184-byte packet is groupedto create a data group having a pre-determined size. Subsequently, thepacket deformatter 456 removes the known data from pre-decided places,the known data having been inserted in an earlier process by thetransmitting system for the demodulation and equalization processes.Then, the packet deformatter 456 identifies the enhanced data includedin the head, body, and tail areas within the data group and outputs theidentified enhanced data to the enhanced data processor 457.

The enhanced data processor 457 performs block deinterleaving and blockdecoding processes on the soft-decided and outputted enhanced data. Morespecifically, the enhanced data processor 457 performs the inverseprocesses of the pre-processor included in the transmitting system. Forexample, it is assumed that the pre-processor of the transmitting systemhas separately performed an additional block encoding process, a blockinterleaving process, and a byte expansion by either adding null bits orby repeating the input bits on the inputted enhanced data depending uponthe enhanced data type. Accordingly, the enhanced data processor 457separately performs the inverse processes of the pre-processor includedin the transmitting system on the enhanced data depending upon theenhanced data type. Similarly, the final enhanced data identified basedupon the order of importance or priority, in accordance with the samemethod as in the transmitting system, are then outputted. Morespecifically, the enhanced data processor 457 processes the enhanceddata soft-decided and inputted by removing the null bits or repetitionbits that have been inserted by the pre-processor for byte expansion andperforming block deinterleaving and block decoding processes inaccordance with the enhanced data type. Thereafter, the enhanced dataprocessor 457 outputs the final enhanced data. For example, the finalenhanced data are identified as high priority enhanced data and lowpriority enhanced data and then outputted.

Meanwhile, in the receiving system shown in FIG. 4, a signal position(or place) should first be acknowledged within the transmission dataframe in order to allow the transmitted signal to be received withreliability. Therefore, the known data detector and initial frequencyoffset estimator 430 acquires initial synchronization by using thetransmitted known data. The demodulator 420 should compensate relativemovements of the transmitting system and the receiving system and acarrier frequency offset and a sampling frequency offset that aregenerated due to a difference in frequency between a transmissionoscillator and a receiving oscillator. Furthermore, the demodulator 420should also perform carrier recovery and timing clock recovery processeson the received signal and should also remove a pilot tone signalinserted from a baseband during the transmission of the signal, therebyinserting the processed signal to the equalizer 440.

FIG. 5 illustrates a detailed block diagram of a demodulator accordingto the present invention. Referring to FIG. 5, the demodulator includesa phase splitter 511, a numerically controlled oscillator (NCO) 512, afirst multiplier 513, a resampler 514, a second multiplier 515, amatched filter 516, a DC remover 517, a decimator 518, a timing recoveryunit 520, a carrier recovery unit 530, and a phase compensator 540.Herein, the timing recovery unit 520 includes a buffer 521, a decimator522, a timing error detector 523, a loop filter 524, a holder 525, and aNCO 526. The carrier recovery unit 530 includes a buffer 531, afrequency offset estimator 532, a loop filter 533, a holder 534, anadder 535, and a NCO 536. Finally, the phase compensator 540 includes abuffer 541, a frequency offset estimator 542, a holder 543, a NCO 544,and a multiplier 545.

Herein, the decimator 518 and 522 each corresponds to a componentrequired when a signal being inputted to the phase compensator 540 isoversampled to N times by the ADC 410. More specifically, the integer Nrepresents the sampling rate of the received signal. For example, whenthe input signal is oversampled to 2 times (i.e., when N=2), thisindicates that two samples are included in one symbol. In this case, thedecimator 518 and 522 corresponds to a ½ decimator. Depending uponwhether or not the oversampling process of the received signal has beenperformed, the signal may bypass the decimator 518 and 522.

Referring to FIG. 5, the phase splitter 511 splits the pass band digitalsignal, which is outputted from the ADC 410, into a pass band digitalsignal of a real number element and a pass band digital signal of animaginary number element both having a phase of −90 degrees between oneanother. In other words, the pass band digital signal is split intocomplex signals. The split portions of the pass band digital signal arethen outputted to the first multiplier 513. Herein, the real numbersignal outputted from the phase splitter 511 will be referred to as an‘I’ signal, and the imaginary number signal outputted from the phasesplitter 511 will be referred to as a ‘Q’ signal, for simplicity of thedescription of the present invention.

The first multiplier 513 multiplies the I and Q pass band digitalsignals, which are outputted from the phase splitter 511, to a complexsignal having a frequency proportional to a constant being outputtedfrom the NCO 512, thereby changing the I and Q pass band digital signalsto baseband digital complex signals. Then, the baseband digital signalsof the first multiplier 513 are inputted to the resampler 514. Theresampler 514 resamples the signals being outputted from the firstmultiplier 513 so that the signal correspond to the timing clockprovided by the NCO 526 of the timing recovery unit 520. Thereafter, theresampler 514 outputs the resampled signals to the second multiplier515.

For example, when the ADC 410 uses a 25 MHz fixed oscillator, thebaseband digital signal having a frequency of 25 MHz, which is createdby passing through the ADC 410, the phase splitter 511, and the firstmultiplier 513, is processed with an interpolation process by theresampler 514. Thus, the interpolated signal is recovered to a basebanddigital signal having a frequency twice that of the receiving signal ofa symbol clock (i.e., a frequency of 21.524476 MHz). Alternatively, ifthe ADC 410 uses the sampling frequency as the output frequency of theNCO 526 included in the timing recovery unit 520 (i.e., if the ADC 410uses a variable frequency) in order to perform an A/D conversionprocess, the resampler 514 is not required and may be omitted.

The second multiplier 515 multiplies an output frequency of the NCO 536included in the carrier recovery unit 530 with the output of theresampler 514 so as to compensate any remaining carrier included in theoutput signal of the resampler 514. Thereafter, the compensated carrieris outputted to the matched filter 516 and the timing recovery unit 520.The signal matched-filtered by the matched filter 516 is inputted to theDC remover 517, the known data detector and initial frequency offsetestimator 430, and the carrier recovery unit 530.

The known data detector and initial frequency offset estimator 430detects the place (o position) of the known data sequences that arebeing periodically or non-periodically transmitted. Simultaneously, theknown data detector and initial frequency offset estimator 430 estimatesan initial frequency offset during the known data detection process.More specifically, while the transmission data frame is being received,the known data detector and initial frequency offset estimator 430detects the position (or place) of the known data included in thetransmission data frame. Then, the known data detector and initialfrequency offset estimator 430 outputs the detected information on theknown data place (i.e., a known sequence position indicator) to thetiming recovery unit 520, the carrier recovery unit 530, and the phasecompensator 540 of the demodulator 420. Furthermore, the known datadetector and initial frequency offset estimator 430 estimates theinitial frequency offset, which is then outputted to the carrierrecovery unit 530. At this point, the known data detector and initialfrequency offset estimator 430 may either receive the output of thematched filter 516 or receive the output of the resampler 514. This maybe optionally decided depending upon the design of the system designer.

FIG. 6 illustrates a detailed block diagram showing a known data (orsequence) detector and generator according to an embodiment of thepresent invention. More specifically, FIG. 6 illustrates an example ofan initial frequency offset being estimated along with the knownsequence position indicator. Herein, FIG. 6 shows an example of aninputted signal being oversampled to N times of its initial state.Referring to FIG. 6, the known sequence detector and generator includesN number of partial correlators 611 to 61N configured in parallel, aknown data place detector and frequency offset decider 620, a known dataextractor 630, a buffer 640, a multiplier 650, a NCO 660, a frequencyoffset estimator 670, and an adder 680. Herein, the first partialcorrelator 611 consists of a 1/N decimator, and a partial correlator.The second partial correlator 612 consists of a 1 sample delay, a 1/Ndecimator, and a partial correlator. And, the N^(th) partial correlator61N consists of a N−1 sample delay, a 1/N decimator, and a partialcorrelator. These are used to match (or identify) the phase of each ofthe samples within the oversampled symbol with the phase of the original(or initial) symbol, and to decimate the samples of the remainingphases, thereby performing partial correlation on each sample. Morespecifically, the input signal is decimated at a rate of 1/N for eachsampling phase, so as to pass through each partial correlator.

For example, when the input signal is oversampled to 2 times (i.e., whenN=2), this indicates that two samples are included in one signal. Inthis case, two partial correlators are required, and each 1/N decimatorbecomes a ½ decimator. At this point, the 1/N decimator of the firstpartial correlator 611 decimates (or removes), among the input samples,the samples located in-between symbol places (or positions). Then, thecorresponding 1/N decimator outputs the decimated sample to the partialcorrelator. Furthermore, the 1 sample delay of the second partialcorrelator 612 delays the input sample by 1 sample (i.e., performs a 1sample delay on the input sample) and outputs the delayed input sampleto the 1/N decimator. Subsequently, among the samples inputted from the1 sample delay, the 1/N decimator of the second partial correlator 612decimates (or removes) the samples located in-between symbol places (orpositions). Thereafter, the corresponding 1/N decimator outputs thedecimated sample to the partial correlator.

After each predetermined period of the symbol, each of the partialcorrelators outputs a correlation value and an estimation value of thecoarse frequency offset estimated at that particular moment to the knowndata place detector and frequency offset decider 620. The known dataplace detector and frequency offset decider 620 stores the output of thepartial correlators corresponding to each sampling phase during a datagroup cycle or a pre-decided cycle. Thereafter, the known data placedetector and frequency offset decider 820 decides a position (or place)corresponding to the highest correlation value, among the stored values,as the place (or position) for receiving the known data. Simultaneously,the known data place detector and frequency offset decider 620 finallydecides the estimation value of the frequency offset estimated at themoment corresponding to the highest correlation value as the coarsefrequency offset value of the receiving system. At this point, the knownsequence position indicator is inputted to the known data extractor 630,and the estimated coarse frequency offset is inputted to the adder 680and the NCO 660.

In the meantime, while the N number of partial correlators 611 to 61Ndetect the known data place (or known sequence position) and estimatethe coarse frequency offset, the buffer 640 temporarily stores thereceived data and outputs the temporarily stored data to the known dataextractor 630. The known data extractor 630 uses the known sequenceposition indicator, which is outputted from the known data placedetector and frequency offset decider 620, so as to extract the knowndata from the output of the buffer 640. Thereafter, the known dataextractor 630 outputs the extracted data to the multiplier 650. The NCO660 generates a complex signal corresponding to the coarse frequencyoffset being outputted from the known data place detector and frequencyoffset decider 620. Then, the NCO 660 outputs the generated complexsignal to the multiplier 650.

The multiplier 650 multiplies the complex signal of the NCO 660 to theknown data being outputted from the known data extractor 630, therebyoutputting the known data having the coarse frequency offset compensatedto the frequency offset estimator 670. The frequency offset estimator670 estimates a fine frequency offset from the known data having thecoarse frequency offset compensated. Subsequently, the frequency offsetestimator 670 outputs the estimated fine frequency offset to the adder680. The adder 680 adds the coarse frequency offset to the finefrequency offset. Thereafter, the adder 680 decides the added result asa final initial frequency offset, which is then outputted to the adder535 of the carrier recovery unit 530 included in the demodulator 420.More specifically, during the process of acquiring initialsynchronization, the present invention may estimate and use the coarsefrequency offset as well as the fine frequency offset, thereby enhancingthe estimation performance of the initial frequency offset.

It is assumed that the known data is inserted within the data group andthen transmitted, as shown in FIG. 2. Then, the known data detector andinitial frequency offset estimator 430 may use the known data that havebeen additionally inserted at the beginning portion of the body area, soas to estimate the initial frequency offset. The known positionindicator, which was periodically inserted within the body areaestimated by the known data detector and initial frequency offsetestimator 430, is inputted to the timing error detector 523 of thetiming error recovery unit 420, to the frequency offset estimator 532 ofthe carrier recovery unit 530, and to the frequency offset estimator 542of the phase compensator 540. More specifically, the output of thesecond multiplier 515 is temporarily stored in the buffer 521 within thetiming recovery unit 520. Subsequently, the temporarily stored outputdata are inputted to the timing error detector 523 through the decimator522.

Assuming that the output of the second multiplier 515 is oversampled toN times its initial state, the decimator 522 decimates the output of thebuffer 521 at a decimation rate of 1/N. Then, the 1/N-decimated data areinputted to the timing error detector 523. In other words, the decimator522 performs decimation on the input signal in accordance with a symbolcycle. Furthermore, the buffer 521 may also receive the output of thematched filter 516 instead of the output of the second multiplier 515.The timing error detector 523 uses the known sequence position indicatorto detect a timing error from the known data sequence prior to or afterbeing processed with matched-filtering, when the known data sequence isbeing inputted. Thereafter, the detected timing error is outputted tothe loop filter 524. Accordingly, the detected timing error informationis obtained once during each repetition cycle of the known datasequence. More specifically, for example, if a known data sequencehaving the same pattern is periodically inserted and transmitted, asshown in FIG. 3, the timing error detector 523 may use the known data inorder to detect the timing error.

There exists a plurality of methods for detecting timing error by usingthe known data. In the example of the present invention, the timingerror may be detected by using a correlation characteristic between theknown data and the received data in the time domain, the known databeing already known in accordance with a pre-arranged agreement betweenthe transmitting system and the receiving system. The timing error mayalso be detected by using the correlation characteristic of the twoknown data types being received in the frequency domain. Thus, thedetected timing error is outputted. In another example, a spectrallining method may be applied in order to detect the timing error.Herein, the spectral lining method corresponds to a method of detectingtiming error by using sidebands of the spectrum included in the receivedsignal.

The loop filter 524 filters the timing error detected by the timingerror detector 523 and, then, outputs the filtered timing error to theholder 525. The holder 525 holds (or maintains) the timing errorfiltered and outputted from the loop filter 524 during a pre-determinedknown data sequence cycle period and outputs the processed timing errorto the NCO 526. The NCO 526 accumulates the timing error outputted fromthe holder 525. Thereafter, the NCO 526 outputs the phase element of theaccumulated timing error to the resampler 514, thereby adjusting thesampling timing of the resampler 514. More specifically, a signal havingthe correct phase is to be interpolated and outputted from the resampler514. Herein, the positions of the loop filter 524 and the holder 526 maybe switched from one to the other.

Meanwhile, the buffer 531 of the carrier recovery unit 530 may receiveeither the data inputted to the matched filter 416 or the data outputtedfrom the matched filter 416 and, then, temporarily store the receiveddata. Thereafter, the temporarily stored data are outputted to thefrequency offset estimator 532. The frequency offset estimator 532 usesthe known sequence position indicator outputted from the known datadetector and initial frequency offset estimator 430 in order to estimatethe frequency offset from the known data sequence prior to or aftermatched-filtering, when the known data sequence is being inputted. Then,the estimated frequency offset is outputted to the loop filter 533.Therefore, the estimated frequency offset value is obtained once everyrepetition period of the known data sequence.

The loop filter 533 performs low pass filtering on the frequency offsetvalue estimated by the frequency offset estimator 532 and outputs thelow pass-filtered frequency offset value to the holder 534. The holder534 holds (or maintains) the low pass-filtered frequency offset valueduring a pre-determined known data sequence cycle period and outputs thefrequency offset value to the adder 535. Herein, the positions of theloop filter 533 and the holder 534 may be switched from one to theother. The adder 535 adds the value of the initial frequency offsetestimated by the known data detector and initial frequency offsetestimator 430 to the frequency offset value outputted from the holder534. Thereafter, the added offset value is outputted to the NCO 536.

The NCO 536 generates a complex signal corresponding to the frequencyoffset outputted from the adder 535, which is then outputted to thesecond multiplier 515. The second multiplier 515 multiplies the outputof the NCO 536 included in the carrier recovery unit 530 to the outputof the resampler 514, so as to remove the carrier offset included in theoutput signal of the resample 514. Meanwhile, the DC remover 517 removesthe pilot tone that had been inserted during the transmission processfrom the matched-filtered signal. Thereafter, the processed signal isoutputted to the phase compensator 540.

FIG. 7 illustrates a detailed block diagram of a DC remover according toan embodiment of the present invention. Herein, identical signalprocessing processes are performed on each of a real number element (orin-phase (I)) and an imaginary number element (or a quadrature (Q)) ofthe inputted complex signal, thereby estimating and removing the DCvalue of each element. In order to do so, the DC remover shown in FIG. 7includes a first DC estimator and remover 710 and a second DC estimatorand remover 720. Herein, the first DC estimator and remover 710 includesan L sample buffer 711, a DC estimator 712, an M sample holder 713, a Csample delay 714, and a subtractor 715.

The first DC estimator and remover 710 estimates and removes the DC ofthe real number element (i.e., an in-phase DC). Furthermore, the secondDC estimator and remover 720 includes an L sample buffer 721, a DCestimator 722, an M sample holder 723, a C sample delay 724, and asubtractor 725. The second DC estimator and remover 720 estimates andremoves the DC of the imaginary number element (i.e., a quadrature DC).In the present invention, the first DC estimator and remover 710 and thesecond DC estimator and remover 720 may receive different input signals.However, each DC estimator and remover 710 and 720 has the samestructure. Therefore, a detailed description of the first DC estimatorand remover 710 will be presented herein, and the second DC estimatorand remover 720 will be omitted for simplicity.

More specifically, the in-phase signal matched-filtered by the matchedfilter 516 is inputted to the L sample buffer 711 of the first DCestimator and remover 710 within the DC remover 517 and is then stored.The L sample buffer 711 is a buffer having the length of L sample thesecond DC estimator and remover 720. Herein, the output of the L samplebuffer 711 is inputted to the DC estimator 712 and the C sample delay714. The DC estimator 712 uses the data having the length of L sample,which are outputted from the buffer 711, so as to estimate the DC valueby using Equation 1 shown below.

$\begin{matrix}{{y\lbrack n\rbrack} = {\frac{1}{L}{\sum\limits_{k = 0}^{L - 1}\;{x\left\lbrack {k + {M \times n}} \right\rbrack}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the above-described Equation 1, x[n] represents the inputted sampledata stored in the buffer 711. And, y[n] indicates the DC estimationvalue. More specifically, the DC estimator 712 accumulates L number ofsample data stored in the buffer 711 and estimates the DC value bydividing the accumulated value by L. At this point, the stored inputsample data set is shifted as much as M sample. Herein, the DCestimation value is outputted once every M samples.

FIG. 8 illustrates a shifting of the input sample data used for DCestimation. For example, when M is equal to 1 (i.e., M=1), the DCestimator 712 estimates the DC value each time a sample is shifted tothe buffer 711. Accordingly, each estimated result is outputted for eachsample. If M is equal to L (i.e., ML), the DC estimator 712 estimatesthe DC value each time L number of samples are shifted to the buffer711. Accordingly, each estimated result is outputted for each cycle of Lsamples. Therefore, in this case, the DC estimator 712 corresponds to aDC estimator that operates in a block unit of L samples. Herein, anyvalue within the range of 1 and L may correspond to the value M.

As described above, since the output of the DC estimator 712 isoutputted after each cycle of M samples, the M sample holder 713 holdsthe DC value estimated from the DC estimator 712 for a period of Msamples. Then, the estimated DC value is outputted to the subtractor715. Also, the C sample delay 714 delays the input sample data stored inthe buffer 711 by C samples, which are then outputted to the subtractor715. The subtractor 715 subtracts the output of the M sample holder 713from the output of the C sample delay 714. Thereafter, the subtractor715 outputs the signal having the in-phase DC removed.

Herein, the C sample delay 714 decides which portion of the input sampledata is to be compensated with the output of the DC estimator 712. Morespecifically, the DC estimator and remover 710 may be divided into a DCestimator 712 for estimating the DC and the subtractor for compensatingthe input sample data within the estimated DC value. At this point, theC sample delay 714 decides which portion of the input sample data is tobe compensated with the estimated DC value. For example, when C is equalto 0 (i.e., C=0), the beginning of the L samples is compensated with theestimated DC value obtained by using L samples. Alternatively, when C isequal to L (i.e., C=L), the end of the L samples is compensated with theestimated DC value obtained by using L samples.

Similarly, the data having the DC removed by the DC remover 517 areinputted to the buffer 541 and the frequency offset estimator 542 of thephase compensator 540. The frequency offset estimator 542 uses the knownsequence position indicator outputted from the known data detector andinitial frequency offset estimator 430 in order to estimate thefrequency offset from the known data sequence that is being inputted,the known data sequence having the DC removed by the DC remover 517.Then, the frequency offset estimator 542 outputs the estimated frequencyoffset to the holder 543. Similarly, the frequency offset estimationvalue is obtained at each repetition cycle of the known data sequence.

Therefore, the holder 543 holds the frequency offset estimation valueduring a cycle period of the known data sequence and then outputs thefrequency offset estimation value to the NCO 544. The NCO 544 generatesa complex signal corresponding to the frequency offset held by theholder 543 and outputs the generated complex signal to the multiplier545. The multiplier 545 multiplies the complex signal outputted from theNCO 544 to the data being delayed by a set period of time in the buffer541, thereby compensating the phase change included in the delayed data.The data having the phase change compensated by the multiplier 545 passthrough the decimator 518 so as to be inputted to the equalizer 440. Atthis point, since the frequency offset estimated by the frequency offsetestimator of the phase compensator 540 does not pass through the loopfilter, the estimated frequency offset indicates the phase differencebetween the known data sequences. In other words, the estimatedfrequency offset indicates a phase offset.

FIG. 9 illustrates a block diagram showing the structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention. The digital broadcast (or DTV) transmitting system includes apre-processor 810, a packet multiplexer 821, a data randomizer 822, aReed-Solomon (RS) encoder/non-systematic RS encoder 823, a datainterleaver 824, a parity byte replacer 825, a non-systematic RS encoder826, a frame multiplexer 828, and a transmitting system 830. Thepre-processor 810 includes an enhanced data randomizer 811, a RS frameencoder 812, a block processor 813, a group formatter 814, a datadeinterleaver 815, and a packet formatter 816.

In the present invention having the above-described structure, main dataare inputted to the packet multiplexer 821. Enhanced data are inputtedto the enhanced data randomizer 811 of the pre-processor 810, wherein anadditional coding process is performed so that the present invention canrespond swiftly and appropriately against noise and change in channel.The enhanced data randomizer 811 randomizes the received enhanced dataand outputs the randomized enhanced data to the RS frame encoder 812. Atthis point, by having the enhanced data randomizer 811 perform therandomizing process on the enhanced data, the randomizing process on theenhanced data by the data randomizer 822 in a later process may beomitted. Either the randomizer of the conventional broadcast system maybe used as the randomizer for randomizing the enhanced data, or anyother type of randomizer may be used herein.

The RS frame encoder 812 receives the randomized enhanced data andperforms at least one of an error correction coding process and an errordetection coding process on the received data. Accordingly, by providingrobustness to the enhanced data, the data can scatter group error thatmay occur due to a change in the frequency environment. Thus, the datacan respond appropriately to the frequency environment which is verypoor and liable to change. The RS frame encoder 812 also includes aprocess of mixing in row units many sets of enhanced data each having apre-determined size. By performing an error correction coding process onthe inputted enhanced data, the RS frame encoder 812 adds data requiredfor the error correction and, then, performs an error detection codingprocess, thereby adding data required for the error detection process.The error correction coding uses the RS coding method, and the errordetection coding uses the cyclic redundancy check (CRC) coding method.When performing the RS coding process, parity data required for theerror correction are generated. And, when performing the CRC codingprocess, CRC data required for the error detection are generated.

The RS frame encoder 812 performs CRC coding on the RS coded enhanceddata in order to create the CRC code. The CRC code that is generated bythe CRC coding process may be used to indicate whether the enhanced datahave been damaged by an error while being transmitted through thechannel. The present invention may adopt other types of error detectioncoding methods, apart from the CRC coding method, and may also use theerror correction coding method so as to enhance the overall errorcorrection ability of the receiving system. For example, assuming thatthe size of one RS frame is 187*N bytes, that (235,187)-RS codingprocess is performed on each column within the RS frame, and that a CRCcoding process using a 2-byte (i.e., 16-bit) CRC checksum, then a RSframe having the size of 187*N bytes is expanded to a RS frame of235*(N+2) bytes. The RS frame expanded by the RS frame encoder 812 isinputted to the block processor 813. The block processor 813 codes theRS-coded and CRC-coded enhanced data at a coding rate of M1/N1. Then,the block processor 813 outputs the M1/N1-rate coded enhanced data tothe group formatter 814. In order to do so, the block processor 813identifies the block data bytes being inputted from the RS frame encoder812 as bits.

The block processor 813 may receive supplemental information data suchas signaling information, which include information on the system, andidentifies the supplemental information data bytes as data bits. Herein,the supplemental information data, such as the signaling information,may equally pass through the enhanced data randomizer 811 and the RSframe encoder 812 so as to be inputted to the block processor 813.Alternatively, the supplemental information data may be directlyinputted to the block processor 813 without passing through the enhanceddata randomizer 811 and the RS frame encoder 812. The signalinginformation corresponds to information required for receiving andprocessing data included in the data group in the receiving system. Suchsignaling information includes data group information, multiplexinginformation, and burst information.

As a M1/N1-rate encoder, the block processor 813 codes the inputted dataat a coding rate of M1/N1 and then outputs the M1/N1-rate coded data.For example, if 1 bit of the input data is coded to 2 bits andoutputted, then M1 is equal to 1 and N1 is equal to 2 (i.e., M1=1 andN1=2). Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then M1 is equal to 1 and N1 is equal to 4 (i.e., M1=1 andN1=4). As an example of the present invention, it is assumed that theblock processor 813 performs a coding process at a coding rate of ½(also referred to as a ½-rate coding process) or a coding process at acoding rate of ¼ (also referred to as a ¼-rate coding process). Morespecifically, the block processor 813 codes the received enhanced dataand supplemental information data, such as the signaling information, ateither a coding rate of ½ or a coding rate of ¼. Thereafter, thesupplemental information data, such as the signaling information, areidentified and processed as enhanced data.

Since the ¼-rate coding process has a higher coding rate than the ½-ratecoding process, greater error correction ability may be provided.Therefore, in a later process, by allocating the ¼-rate coded data in anarea with deficient receiving performance within the group formatter814, and by allocating the ½-rate coded data in an area with excellentreceiving performance, the difference in the overall performance may bereduced. More specifically, in case of performing the ½-rate codingprocess, the block processor 813 receives 1 bit and codes the received 1bit to 2 bits (i.e., 1 symbol). Then, the block processor 813 outputsthe processed 2 bits (or 1 symbol). On the other hand, in case ofperforming the ¼-rate coding process, the block processor 813 receives 1bit and codes the received 1 bit to 4 bits (i.e., 2 symbols). Then, theblock processor 813 outputs the processed 4 bits (or 2 symbols).Additionally, the block processor 813 performs a block interleavingprocess in symbol units on the symbol-coded data. Subsequently, theblock processor 813 converts to bytes the data symbols that areblock-interleaved and have the order rearranged.

The group formatter 814 inserts the enhanced data outputted from theblock processor 813 (herein, the enhanced data may include supplementalinformation data such as signaling information including transmissioninformation) in a corresponding area within the data group, which isconfigured according to a pre-defined rule. Furthermore, in relationwith the data deinterleaving process, various types of places holders orknown data are also inserted in corresponding areas within the datagroup. At this point, the data group may be described by at least onehierarchical area. Herein, the data allocated to the each area may varydepending upon the characteristic of each hierarchical area.Additionally, each data group may be configured to include a fieldsynchronization signal.

In another example given in the present invention, a data group isdivided into A, B, and C regions in a data configuration prior to datadeinterleaving.

FIG. 10 illustrates an alignment of data before being data deinterleavedand identified, and FIG. 11 illustrates an alignment of data after beingdata deinterleaved and identified. More specifically, a data structureidentical to that shown in FIG. 10 is transmitted to a receiving system.Also, the data group configured to have the same structure as the datastructure shown in FIG. 10 is inputted to the data deinterleaver 815.

As described above, FIG. 10 illustrates a data structure prior to datadeinterleaving that is divided into 3 regions, such as region A, regionB, and region C. Also, in the present invention, each of the regions Ato C is further divided into a plurality of regions. Referring to FIG.10, region A is divided into 5 regions (A1 to A5), region B is dividedinto 2 regions (B1 and B2), and region C is divided into 3 regions (C1to C3). Herein, regions A to C are identified as regions having similarreceiving performances within the data group. Herein, the type ofenhanced data, which are inputted, may also vary depending upon thecharacteristic of each region.

In the example of the present invention, the data structure is dividedinto regions A to C based upon the level of interference of the maindata. Herein, the data group is divided into a plurality of regions tobe used for different purposes. More specifically, a region of the maindata having no interference or a very low interference level may beconsidered to have a more resistant (or stronger) receiving performanceas compared to regions having higher interference levels. Additionally,when using a system inserting and transmitting known data in the datagroup, and when consecutively long known data are to be periodicallyinserted in the enhanced data, the known data having a predeterminedlength may be periodically inserted in the region having no interferencefrom the main data (e.g., region A). However, due to interference fromthe main data, it is difficult to periodically insert known data andalso to insert consecutively long known data to a region havinginterference from the main data (e.g., region B and region C).

Hereinafter, examples of allocating data to region A (A1 to A5), regionB (B1 and B2), and region C (C1 to C3) will now be described in detailwith reference to FIG. 10. The data group size, the number ofhierarchically divided regions within the data group and the size ofeach region, and the number of enhanced data bytes that can be insertedin each hierarchically divided region of FIG. 10 are merely examplesgiven to facilitate the understanding of the present invention. Herein,the group formatter 814 creates a data group including places in whichfield synchronization bytes are to be inserted, so as to create the datagroup that will hereinafter be described in detail.

More specifically, region A is a region within the data group in which along known data sequence may be periodically inserted, and in whichincludes regions wherein the main data are not mixed (e.g., A1 to A5).Also, region A includes a region (e.g., A1) located between a fieldsynchronization region and the region in which the first known datasequence is to be inserted. The field synchronization region has thelength of one segment (i.e., 832 symbols) existing in an ATSC system.

For example, referring to FIG. 10, 2428 bytes of the enhanced data maybe inserted in region A1, 2580 bytes may be inserted in region A2, 2772bytes may be inserted in region A3, 2472 bytes may be inserted in regionA4, and 2772 bytes may be inserted in region A5. Herein, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. As described above, when region Aincludes a known data sequence at both ends, the receiving system useschannel information that can obtain known data or field synchronizationdata, so as to perform equalization, thereby providing enforcedequalization performance.

Also, region B includes a region located within 8 segments at thebeginning of a field synchronization region within the data group(chronologically placed before region A1) (e.g., region B1), and aregion located within 8 segments behind the very last known datasequence which is inserted in the data group (e.g., region B2). Forexample, 1130 bytes of the enhanced data may be inserted in the regionB1, and 1350 bytes may be inserted in region B2. Similarly, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. In case of region B, the receiving systemmay perform equalization by using channel information obtained from thefield synchronization section. Alternatively, the receiving system mayalso perform equalization by using channel information that may beobtained from the last known data sequence, thereby enabling the systemto respond to the channel changes.

Region C includes a region located within 30 segments including andpreceding the 9^(th) segment of the field synchronization region(chronologically located before region A) (e.g., region C1), a regionlocated within 12 segments including and following the 9^(th) segment ofthe very last known data sequence within the data group (chronologicallylocated after region A) (e.g., region C2), and a region located in 32segments after the region C2 (e.g., region C3). For example, 1272 bytesof the enhanced data may be inserted in the region C1, 1560 bytes may beinserted in region C2, and 1312 bytes may be inserted in region C3.Similarly, trellis initialization data or known data, MPEG header, andRS parity are not included in the enhanced data. Herein, region C (e.g.,region C1) is located chronologically earlier than (or before) region A.

Since region C (e.g., region C1) is located further apart from the fieldsynchronization region which corresponds to the closest known dataregion, the receiving system may use the channel information obtainedfrom the field synchronization data when performing channelequalization. Alternatively, the receiving system may also use the mostrecent channel information of a previous data group. Furthermore, inregion C (e.g., region C2 and region C3) located before region A, thereceiving system may use the channel information obtained from the lastknown data sequence to perform equalization. However, when the channelsare subject to fast and frequent changes, the equalization may not beperformed perfectly. Therefore, the equalization performance of region Cmay be deteriorated as compared to that of region B.

When it is assumed that the data group is allocated with a plurality ofhierarchically divided regions, as described above, the block processor813 may encode the enhanced data, which are to be inserted to eachregion based upon the characteristic of each hierarchical region, at adifferent coding rate. For example, the block processor 813 may encodethe enhanced data, which are to be inserted in regions A1 to A5 ofregion A, at a coding rate of ½. Then, the group formatter 814 mayinsert the ½-rate encoded enhanced data to regions A1 to A5.

The block processor 813 may encode the enhanced data, which are to beinserted in regions B1 and B2 of region B, at a coding rate of ¼ havinghigher error correction ability as compared to the ½-coding rate. Then,the group formatter 814 inserts the ¼-rate coded enhanced data in regionB1 and region B2. Furthermore, the block processor 813 may encode theenhanced data, which are to be inserted in regions C1 to C3 of region C,at a coding rate of ¼ or a coding rate having higher error correctionability than the ¼-coding rate. Then, the group formatter 814 may eitherinsert the encoded enhanced data to regions C1 to C3, as describedabove, or leave the data in a reserved region for future usage.

In addition, the group formatter 814 also inserts supplemental data,such as signaling information that notifies the overall transmissioninformation, other than the enhanced data in the data group. Also, apartfrom the encoded enhanced data outputted from the block processor 813,the group formatter 814 also inserts MPEG header place holders,non-systematic RS parity place holders, main data place holders, whichare related to data deinterleaving in a later process, as shown in FIG.10. Herein, the main data place holders are inserted because theenhanced data bytes and the main data bytes are alternately mixed withone another in regions B and C based upon the input of the datadeinterleaver, as shown in FIG. 10. For example, based upon the dataoutputted after data deinterleaving, the place holder for the MPEGheader may be allocated at the very beginning of each packet.

Furthermore, the group formatter 814 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoder 827 are also insertedin the corresponding regions. For example, the initialization data placeholders may be inserted in the beginning of the known data sequence.Herein, the size of the enhanced data that can be inserted in a datagroup may vary in accordance with the sizes of the trellisinitialization place holders or known data (or known data placeholders), MPEG header place holders, and RS parity place holders.

The output of the group formatter 814 is inputted to the datadeinterleaver 815. And, the data deinterleaver 815 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 816. More specifically, when the data and place holderswithin the data group configured, as shown in FIG. 10, are deinterleavedby the data deinterleaver 815, the data group being outputted to thepacket formatter 816 is configured to have the structure shown in FIG.11.

Among the data deinterleaved and inputted, the packet formatter 816removes the main data place holder and RS parity place holder that wereallocated for the deinterleaving process from the inputted deinterleaveddata. Thereafter, the remaining portion of the corresponding data isgrouped, and 4 bytes of MPEG header are inserted therein. The 4-byteMPEG header is configured of a 1-byte MPEG synchronization byte added tothe 3-byte MPEG header place holder.

When the group formatter 814 inserts the known data place holder, thepacket formatter 816 may either insert actual known data in the knowndata place holder or output the known data place holder without anychange or modification for a replacement insertion in a later process.Afterwards, the packet formatter 816 divides the data within theabove-described packet-formatted data group into 188-byte unit enhanceddata packets (i.e., MPEG TS packets), which are then provided to thepacket multiplexer 821. The packet multiplexer 821 multiplexes the188-byte unit enhanced data packet and main data packet outputted fromthe packet formatter 816 according to a pre-defined multiplexing method.Subsequently, the multiplexed data packets are outputted to the datarandomizer 822. The multiplexing method may be modified or altered inaccordance with diverse variables of the system design.

As an example of the multiplexing method of the packet multiplexer 821,the enhanced data burst section and the main data section may beidentified along a time axis (or a chronological axis) and may bealternately repeated. At this point, the enhanced data burst section maytransmit at least one data group, and the main data section may transmitonly the main data. The enhanced data burst section may also transmitthe main data. If the enhanced data are outputted in a burst structure,as described above, the receiving system receiving only the enhanceddata may turn the power on only during the burst section so as toreceive the enhanced data, and may turn the power off during the maindata section in which main data are transmitted, so as to prevent themain data from being received, thereby reducing the power consumption ofthe receiving system.

When the data being inputted correspond to the main data packet, thedata randomizer 822 performs the same randomizing process of theconventional randomizer. More specifically, the MPEG synchronizationbyte included in the main data packet is discarded and a pseudo randombyte generated from the remaining 187 bytes is used so as to randomizethe data. Thereafter, the randomized data are outputted to the RSencoder/non-systematic RS encoder 823. However, when the inputted datacorrespond to the enhanced data packet, the MPEG synchronization byte ofthe 4-byte MPEG header included in the enhanced data packet isdiscarded, and data randomizing is performed only on the remaining3-byte MPEG header. Randomizing is not performed on the remainingportion of the enhanced data. Instead, the remaining portion of theenhanced data is outputted to the RS encoder/non-systematic RS encoder823. This is because the randomizing process has already been performedon the enhanced data by the enhanced data randomizer 811 in an earlierprocess. Herein, a data randomizing process may or may not be performedon the known data (or known data place holder) and the initializationdata place holder included in the enhanced data packet.

The RS encoder/non-systematic RS encoder 823 RS-codes the datarandomized by the data randomizer 822 or the data bypassing the datarandomizer 822. Then, the RS encoder/non-systematic RS encoder 823 addsa 20-byte RS parity to the coded data, thereby outputting theRS-parity-added data to the data interleaver 824. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 823 performs a systematic RS-codingprocess identical to that of the conventional receiving system on theinputted data, thereby adding the 20-byte RS parity at the end of the187-byte data. Alternatively, if the inputted data correspond to theenhanced data packet, the 20 bytes of RS parity gained by performing thenon-systematic RS-coding are respectively inserted in the decided paritybyte places within the enhanced data packet. Herein, the datainterleaver 824 corresponds to a byte unit convolutional interleaver.The output of the data interleaver 824 is inputted to the parity bytereplacer 825 and the non-systematic RS encoder 826.

Meanwhile, a memory within the trellis encoding module 827, which ispositioned after the parity byte replacer 825, should first beinitialized in order to allow the output data of the trellis encodingmodule 827 so as to become the known data defined based upon anagreement between the receiving system and the transmitting system. Morespecifically, the memory of the trellis encoding module 827 should firstbe initialized before the known data sequence being inputted istrellis-encoded. At this point, the beginning of the known data sequencethat is inputted corresponds to the initialization data place holderinserted by the group formatter 814 and not the actual known data.Therefore, a process of generating initialization data right before thetrellis-encoding of the known data sequence being inputted and a processof replacing the initialization data place holder of the correspondingtrellis encoding module memory with the newly generated initializationdata are required.

A value of the trellis memory initialization data is decided based uponthe memory status of the trellis encoding module 827, thereby generatingthe trellis memory initialization data accordingly. Due to the influenceof the replace initialization data, a process of recalculating the RSparity, thereby replacing the RS parity outputted from the trellisencoding module 827 with the newly calculated RS parity is required.Accordingly, the non-systematic RS encoder 826 receives the enhanceddata packet including the initialization data place holder that is to bereplaced with the initialization data from the data interleaver 824 andalso receives the initialization data from the trellis encoding module827. Thereafter, among the received enhanced data packet, theinitialization data place holder is replaced with the initializationdata. Subsequently, the RS parity data added to the enhanced data packetare removed. Then, a new non-systematic RS parity is calculated andoutputted to the parity byte replacer 825. Accordingly, the parity bytereplacer 825 selects the output of the data interleaver 824 as the datawithin the enhanced data packet, and selects the output of thenon-systematic RS encoder 826 as the RS parity. Thereafter, the paritybyte replacer 825 outputs the selected data.

Meanwhile, if the main data packet is inputted, or if the enhanced datapacket that does not include the initialization data place holder thatis to be replaced, the parity byte replacer 825 selects the data and RSparity outputted from the data interleaver 824 and directly outputs theselected data to the trellis encoding module 827 without modification.The trellis encoding module 827 converts the byte-unit data tosymbol-unit data and 12-way interleaves and trellis-encodes theconverted data, which are then outputted to the frame multiplexer 828.The frame multiplexer 828 inserts field synchronization and segmentsynchronization signals in the output of the trellis encoding module 827and then outputs the processed data to the transmitting unit 830.Herein, the transmitting unit 830 includes a pilot inserter 831, amodulator 832, and a radio frequency (RF) up-converter 833. Theoperation of the transmitting unit 830 is identical to the conventionaltransmitters. Therefore, a detailed description of the same will beomitted for simplicity.

FIG. 12 illustrates a block diagram of a demodulating unit included inthe receiving system according to another embodiment of the presentinvention. Herein, the demodulating unit may effectively process signalstransmitted from the transmitting system shown in FIG. 9. Referring toFIG. 12, the demodulating unit includes a demodulator 901, a channelequalizer 902, a known data detector 903, a block decoder 904, anenhanced data deformatter 905, a RS frame decoder 906, an enhanced dataderandomizer 907, a data deinterleaver 908, a RS decoder 909, and a maindata derandomizer 910. For simplicity, the demodulator 901, the channelequalizer 902, the known data detector 903, the block decoder 904, theenhanced data deformatter 905, the RS frame decoder 906, and theenhanced data derandomizer 907 will be referred to as an enhanced dataprocessor. And, the data deinterleaver 908, the RS decoder 909, and themain data derandomizer 910 will be referred to as a main data processor.

More specifically, the enhanced data including known data and the maindata are received through the tuner and inputted to the demodulator 901and the known data detector 903. The demodulator 901 performs automaticgain control, carrier wave recovery, and timing recovery on the datathat are being inputted, thereby creating baseband data, which are thenoutputted to the equalizer 902 and the known data detector 903. Theequalizer 902 compensates the distortion within the channel included inthe demodulated data. Then, the equalizer 902 outputs the compensateddata to the block decoder 904.

At this point, the known data detector 903 detects the known data placeinserted by the transmitting system to the input/output data of thedemodulator 901 (i.e., data prior to demodulation or data afterdemodulation). Then, along with the position information, the known datadetector 903 outputs the symbol sequence of the known data generatedfrom the corresponding position to the demodulator 901 and the equalizer902. Additionally, the known data detector 903 outputs informationenabling the block decoder 904 to identify the enhanced data beingadditionally encoded by the transmitting system and the main data thatare not additionally encoded to the block decoder 904. Furthermore,although the connection is not shown in FIG. 12, the informationdetected by the known data detector 903 may be used in the overallreceiving system and may also be used in the enhanced data formatter 905and the RS frame decoder 906.

By using the known data symbol sequence when performing the timingrecovery or carrier wave recovery, the demodulating performance of thedemodulator 901 may be enhanced. Similarly, by using the known data, thechannel equalizing performance of the channel equalizer 902 may beenhanced. Furthermore, by feeding-back the decoding result of the blockdecoder 904 to the channel equalizer 902, the channel equalizingperformance may also be enhanced.

The channel equalizer 902 may perform channel equalization by using aplurality of methods. An example of estimating a channel impulseresponse (CIR) so as to perform channel equalization will be given inthe description of the present invention. Most particularly, an exampleof estimating the CIR in accordance with each region within the datagroup, which is hierarchically divided and transmitted from thetransmitting system, and applying each CIR differently will also bedescribed herein. Furthermore, by using the known data, the place andcontents of which is known in accordance with an agreement between thetransmitting system and the receiving system, and the fieldsynchronization data, so as to estimate the CIR, the present inventionmay be able to perform channel equalization with more stability.

Herein, the data group that is inputted for the equalization process isdivided into regions A to C, as shown in FIG. 10. More specifically, inthe example of the present invention, each region A, B, and C arefurther divided into regions A1 to A5, regions B1 and B2, and regions C1to C3, respectively. Referring to FIG. 10, the CIR that is estimatedfrom the field synchronization data in the data structure is referred toas CIR_FS. Alternatively, the CIRs that are estimated from each of the 5known data sequences existing in region A are sequentially referred toas CIR_N0, CIR_N1, CIR_N2, CIR_N3, and CIR_N4.

As described above, the present invention uses the CIR estimated fromthe field synchronization data and the known data sequences in order toperform channel equalization on data within the data group. At thispoint, each of the estimated CIRs may be directly used in accordancewith the characteristics of each region within the data group.Alternatively, a plurality of the estimated CIRs may also be eitherinterpolated or extrapolated so as to create a new CIR, which is thenused for the channel equalization process.

Herein, when a value F(Q) of a function F(x) at a particular point Q anda value F(S) of the function F(x) at another particular point S areknown, interpolation refers to estimating a function value of a pointwithin the section between points Q and S. Linear interpolationcorresponds to the simplest form among a wide range of interpolationoperations. The linear interpolation described herein is merelyexemplary among a wide range of possible interpolation methods. And,therefore, the present invention is not limited only to the examples setforth herein.

Alternatively, when a value F(Q) of a function F(x) at a particularpoint Q and a value F(S) of the function F(x) at another particularpoint S are known, extrapolation refers to estimating a function valueof a point outside of the section between points Q and S. Linearextrapolation is the simplest form among a wide range of extrapolationoperations. Similarly, the linear extrapolation described herein ismerely exemplary among a wide range of possible extrapolation methods.And, therefore, the present invention is not limited only to theexamples set forth herein.

More specifically, in case of region C1, any one of the CIR_N4 estimatedfrom a previous data group, the CIR_FS estimated from the current datagroup that is to be processed with channel equalization, and a new CIRgenerated by extrapolating the CIR_FS of the current data group and theCIR_N0 may be used to perform channel equalization. Alternatively, incase of region B1, a variety of methods may be applied as described inthe case for region C1. For example, a new CIR created by linearlyextrapolating the CIR_FS estimated from the current data group and theCIR_N0 may be used to perform channel equalization. Also, the CIR_FSestimated from the current data group may also be used to performchannel equalization. Finally, in case of region A1, a new CIR may becreated by interpolating the CIR_FS estimated from the current datagroup and CIR_N0, which is then used to perform channel equalization.Furthermore, any one of the CIR_FS estimated from the current data groupand CIR_N0 may be used to perform channel equalization.

In case of regions A2 to A5, CIR_N(i−1) estimated from the current datagroup and CIR_N(i) may be interpolated to create a new CIR and use thenewly created CIR to perform channel equalization. Also, any one of theCIR_N(i−1) estimated from the current data group and the CIR_N(i) may beused to perform channel equalization. Alternatively, in case of regionsB2, C2, and C3, CIR_N3 and CIR_N4 both estimated from the current datagroup may be extrapolated to create a new CIR, which is then used toperform the channel equalization process. Furthermore, the CIR_N4estimated from the current data group may be used to perform the channelequalization process. Accordingly, an optimum performance may beobtained when performing channel equalization on the data inserted inthe data group. The methods of obtaining the CIRs required forperforming the channel equalization process in each region within thedata group, as described above, are merely examples given to facilitatethe understanding of the present invention. A wider range of methods mayalso be used herein. And, therefore, the present invention will not onlybe limited to the examples given in the description set forth herein.

Meanwhile, if the data being channel equalized and then inputted to theblock decoder 904 correspond to the enhanced data on which additionalencoding and trellis encoding are both performed by the transmittingsystem, trellis-decoding and additional decoding processes are performedas inverse processes of the transmitting system. Alternatively, if thedata being channel equalized and then inputted to the block decoder 904correspond to the main data on which additional encoding is notperformed and only trellis-encoding is performed by the transmittingsystem, only the trellis-decoding process is performed. The data groupdecoded by the block decoder 904 is inputted to the enhanced datadeformatter 905, and the main data packet is inputted to the datadeinterleaver 908.

More specifically, if the inputted data correspond to the main data, theblock decoder 904 performs Viterbi decoding on the inputted data, so asto either output a hard decision value or hard-decide a soft decisionvalue and output the hard-decided result. On the other hand, if theinputted correspond to the enhanced data, the block decoder 904 outputseither a hard decision value or a soft decision value on the inputtedenhanced data. In other words, if the data inputted to the block decoder904 correspond to the enhanced data, the block decoder 904 performs adecoding process on the data encoded by the block processor and thetrellis encoder of the transmitting system. At this point, the output ofthe RS frame encoder included in the pre-processor of the transmittingsystem becomes an external code, and the output of the block processorand the trellis encoder becomes an internal code. In order to showmaximum performance of the external code when decoding such connectioncodes, the decoder of the internal code should output a soft decisionvalue. Therefore, the block decoder 904 may output a hard decision valueon the enhanced data. However, when required, it is more preferable thatthe block decoder 904 outputs a soft decision value.

The present invention may also be used for configuring a reliability mapusing the soft decision value. The reliability map determines andindicates whether a byte corresponding to a group of 8 bits decided bythe code of the soft decision value is reliable. For example, when anabsolute value of the soft decision value exceeds a pre-determinedthreshold value, the value of the bit corresponding to the soft decisionvalue code is determined to be reliable. However, if the absolute valuedoes not exceed the pre-determined threshold value, then the value ofthe corresponding bit is determined to be not reliable. Further, if atleast one bit among the group of 8 bits, which are determined based uponthe soft decision value, is determined to be not reliable, then thereliability map indicates that the entire byte is not reliable. Herein,the process of determining the reliability by 1-bit units is merelyexemplary. The corresponding byte may also be indicated to be notreliable if a plurality of bits (e.g., 4 bits) is determined to be notreliable.

Conversely, when all of the bits are determined to be reliable withinone byte (i.e., when the absolute value of the soft value of all bitsexceeds the pre-determined threshold value), then the reliability mapdetermines and indicates that the corresponding data byte is reliable.Similarly, when more than 4 bits are determined to be reliable withinone data byte, then the reliability map determines and indicates thatthe corresponding data byte is reliable. The estimated numbers aremerely exemplary and do not limit the scope and spirit of the presentinvention. Herein, the reliability map may be used when performing errorcorrection decoding processes.

Meanwhile, the data deinterleaver 908, the RS decoder 909, and the maindata derandomizer 910 are blocks required for receiving the main data.These blocks may not be required in a receiving system structure thatreceives only the enhanced data. The data deinterleaver 908 performs aninverse process of the data interleaver of the transmitting system. Morespecifically, the data deinterleaver 908 deinterleaves the main databeing outputted from the block decode 904 and outputs the deinterleaveddata to the RS decoder 909. The RS decoder 909 performs systematic RSdecoding on the deinterleaved data and outputs the systematicallydecoded data to the main data derandomizer 910. The main dataderandomizer 910 receives the data outputted from the RS decoder 909 soas to generate the same pseudo random byte as that of the randomizer inthe transmitting system. The main data derandomizer 910 then performs abitwise exclusive OR (XOR) operation on the generated pseudo random databyte, thereby inserting the MPEG synchronization bytes to the beginningof each packet so as to output the data in 188-byte main data packetunits.

Herein, the format of the data being outputted to the enhanced datadeformatter 905 from the block decoder 904 is a data group format. Atthis point, the enhanced data deformatter 905 already knows thestructure of the input data. Therefore, the enhanced data deformatter905 identifies the system information including signaling informationand the enhanced data from the data group. Thereafter, the identifiedsignaling information is transmitted to where the system information isrequired, and the enhanced data are outputted to the RS frame decoder906. The enhanced data deformatter 905 removes the known data, trellisinitialization data, and MPEG header that were included in the main dataand the data group and also removes the RS parity that was added by theRS encoder/non-systematic RS encoder of the transmitting system.Thereafter, the processed data are outputted to the RS frame decoder906.

More specifically, the RS frame decoder 906 receives the RS-coded andCRC-coded enhanced data from the enhanced data deformatter 905 so as toconfigure the RS frame. The RS frame decoder 906 performs an inverseprocess of the RS frame encoder included in the transmitting system,thereby correcting the errors within the RS frame. Then, the 1-byte MPEGsynchronization byte, which was removed during the RS frame codingprocess, is added to the error corrected enhanced data packet.Subsequently, the processed data are outputted to the enhanced dataderandomizer 907. Herein, the enhanced data derandomizer 907 performs aderandomizing process, which corresponds to an inverse process of theenhanced data randomizer included in the transmitting system, on thereceived enhanced data. Then, by outputting the processed data, theenhanced data transmitted from the transmitting system can be obtained.

According to an embodiment of the present invention, the RS framedecoder 906 may also be configured as follows. The RS frame decoder 906may perform a CRC syndrome check on the RS frame, thereby verifyingwhether or not an error has occurred in each row. Subsequently, the CRCchecksum is removed and the presence of an error is indicated on a CRCerror flag corresponding to each row. Then, a RS decoding process isperformed on the RS frame having the CRC checksum removed in a columndirection. At this point, depending upon the number of CRC error flags,a RS erasure decoding process may be performed. More specifically, bychecking the CRC error flags corresponding to each row within the RSframe, the number of CRC error flags may be determined whether it isgreater or smaller than the maximum number of errors, when RS decodingthe number of rows with errors (or erroneous rows) in the columndirection. Herein, the maximum number of errors corresponds to thenumber of parity bytes inserted during the RS decoding process. As anexample of the present invention, it is assumed that 48 parity bytes areadded to each column.

If the number of rows with CRC errors is equal to or smaller than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process is performedon the RS frame in the column direction. Thereafter, the 48 bytes ofparity data that were added at the end of each column are removed.However, if the number of rows with CRC errors is greater than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process cannot beperformed. In this case, the error may be corrected by performing ageneral RS decoding process.

As another embodiment of the present invention, the error correctionability may be enhanced by using the reliability map created whenconfiguring the RS frame from the soft decision value. Morespecifically, the RS frame decoder 906 compares the absolute value ofthe soft decision value obtained from the block decoder 904 to thepre-determined threshold value so as to determine the reliability of thebit values that are decided by the code of the corresponding softdecision value. Then, 8 bits are grouped to configure a byte. Then, thereliability information of the corresponding byte is indicated on thereliability map. Therefore, even if a specific row is determined to haveCRC errors as a result of the CRC syndrome checking process of thecorresponding row, it is not assumed that all of the data bytes includedin the corresponding row have error. Instead, only the data bytes thatare determined to be not reliable, after referring to the reliabilityinformation on the reliability map, are set to have errors. In otherwords, regardless of the presence of CRC errors in the correspondingrow, only the data bytes that are determined to be not reliable (orunreliable) by the reliability map are set as erasure points.

Thereafter, if the number of erasure points for each column is equal toor smaller than the maximum number of errors (e.g., 48), the RS erasuredecoding process is performed on the corresponding the column.Conversely, if the number of erasure points is greater than the maximumnumber of errors (e.g., 48), which may be corrected by the RS erasuredecoding process, a general decoding process is performed on thecorresponding column. In other words, it the number of rows having CRCerrors is greater than the maximum number of errors (e.g., 48), whichmay be corrected by the RS erasure decoding process, either a RS erasuredecoding process or a general RS decoding process is performed on aparticular column in accordance with the number of erasure point withinthe corresponding column, wherein the number is decided based upon thereliability information on the reliability map. When the above-describedprocess is performed, the error correction decoding process is performedin the direction of all of the columns included in the RS frame.Thereafter, the 48 bytes of parity data added to the end of each columnare removed.

FIG. 13 illustrates a block diagram showing the structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention. Referring to FIG. 13, the digital broadcast receiving systemincludes a tuner 1001, a demodulating unit 1002, a demultiplexer 1003,an audio decoder 1004, a video decoder 1005, a native TV applicationmanager 1006, a channel manager 1007, a channel map 1008, a first memory1009, a data decoder 1010, a second memory 1011, a system manager 1012,a data broadcasting application manager 1013, a storage controller 1014,and a third memory 1015. Herein, the third memory 1015 is a mass storagedevice, such as a hard disk drive (HDD) or a memory chip. The tuner 1001tunes a frequency of a specific channel through any one of an antenna,cable, and satellite. Then, the tuner 1001 down-converts the tunedfrequency to an intermediate frequency (IF), which is then outputted tothe demodulating unit 1002. At this point, the tuner 1001 is controlledby the channel manager 1007. Additionally, the result and strength ofthe broadcast signal of the tuned channel are also reported to thechannel manager 1007. The data that are being received by the frequencyof the tuned specific channel include main data, enhanced data, andtable data for decoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 1002 performs demodulation and channelequalization on the signal being outputted from the tuner 1001, therebyidentifying the main data and the enhanced data. Thereafter, theidentified main data and enhanced data are outputted in TS packet units.Examples of the demodulating unit 1002 are shown in FIG. 4 and FIG. 12.The demodulating unit shown in FIG. 4 and FIG. 12 is merely exemplaryand the scope of the present invention is not limited to the examplesset forth herein. In the embodiment given as an example of the presentinvention, only the enhanced data packet outputted from the demodulatingunit 1002 is inputted to the demultiplexer 1003. In this case, the maindata packet is inputted to another demultiplexer (not shown) thatprocesses main data packets. Herein, the storage controller 1014 is alsoconnected to the other demultiplexer in order to store the main dataafter processing the main data packets. The demultiplexer of the presentinvention may also be designed to process both enhanced data packets andmain data packets in a single demultiplexer.

The storage controller 1014 is interfaced with the demultiplexer so asto control instant recording, reserved (or pre-programmed) recording,time shift, and so on of the enhanced data and/or main data. Forexample, when one of instant recording, reserved (or pre-programmed)recording, and time shift is set and programmed in the receiving system(or receiver) shown in FIG. 13, the corresponding enhanced data and/ormain data that are inputted to the demultiplexer are stored in the thirdmemory 1015 in accordance with the control of the storage controller1014. The third memory 1015 may be described as a temporary storage areaand/or a permanent storage area. Herein, the temporary storage area isused for the time shifting function, and the permanent storage area isused for a permanent storage of data according to the user's choice (ordecision).

When the data stored in the third memory 1015 need to be reproduced (orplayed), the storage controller 1014 reads the corresponding data storedin the third memory 1015 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 1003 shown in FIG. 13). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 1015 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 1015 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 1015 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 1014 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 1015 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 1014compression encodes the inputted data and stored the compression-encodeddata to the third memory 1015. In order to do so, the storage controller1014 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 1014.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 1015, the storage controller1014 scrambles the input data and stores the scrambled data in the thirdmemory 1015. Accordingly, the storage controller 1014 may include ascramble algorithm for scrambling the data stored in the third memory1015 and a descramble algorithm for descrambling the data read from thethird memory 1015. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 1003 receives the real-time data outputtedfrom the demodulating unit 1002 or the data read from the third memory1015 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 1003 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 1003 and the subsequent elements.

The demultiplexer 1003 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 1010. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 1010 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PSIP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat are used during the IRD set-up. The NIT may be used for informingor notifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream_typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 1010, thedemultiplexer 1003 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 1010. The demultiplexer 1003 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 1010by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 1003 performs the section filtering process by referringto a table_id field, a version_number field, a section_number field,etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer1003 may output only an application information table (AIT) to the datadecoder 1010 by section filtering. The AIT includes information on anapplication being operated in the receiving system for the data service.The AIT may also be referred to as an XAIT, and an AMT. Therefore, anytable including application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 1011 by the data decoder 1010.

The data decoder 1010 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 1011.The data decoder 1010 groups a plurality of sections having the sametable identification (table_id) so as to configure a table, which isthen parsed. Thereafter, the parsed result is stored as a database inthe second memory 1011. At this point, by parsing data and/or sections,the data decoder 1010 reads all of the remaining actual section datathat are not section-filtered by the demultiplexer 1003. Then, the datadecoder 1010 stores the read data to the second memory 1011. The secondmemory 1011 corresponds to a table and data carousel database storingsystem information parsed from tables and enhanced data parsed from theDSM-CC section. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 1011 or be outputted to thedata broadcasting application manager 1013. In addition, reference maybe made to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 1010 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 1007.

The channel manager 1007 may refer to the channel map 1008 in order totransmit a request for receiving system-related information data to thedata decoder 1010, thereby receiving the corresponding result. Inaddition, the channel manager 1007 may also control the channel tuningof the tuner 1001. Furthermore, the channel manager 1007 may directlycontrol the demultiplexer 1003, so as to set up the A/V PID, therebycontrolling the audio decoder 1004 and the video decoder 1005. The audiodecoder 1004 and the video decoder 1005 may respectively decode andoutput the audio data and video data demultiplexed from the main datapacket. Alternatively, the audio decoder 1004 and the video decoder 1005may respectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 1003 are respectively decoded by the audio decoder1004 and the video decoder 1005. For example, an audio-coding (AC)-3decoding algorithm may be applied to the audio decoder 1004, and aMPEG-2 decoding algorithm may be applied to the video decoder 1005.

Meanwhile, the native TV application manager 1006 operates a nativeapplication program stored in the first memory 1009, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 1006 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 1006 and the databroadcasting application manager 1013. Furthermore, the native TVapplication manager 1006 controls the channel manager 1007, therebycontrolling channel-associated, such as the management of the channelmap 1008, and controlling the data decoder 1010. The native TVapplication manager 1006 also controls the GUI of the overall receivingsystem, thereby storing the user request and status of the receivingsystem in the first memory 1009 and restoring the stored information.

The channel manager 1007 controls the tuner 1001 and the data decoder1010, so as to managing the channel map 1008 so that it can respond tothe channel request made by the user. More specifically, channel manager1007 sends a request to the data decoder 1010 so that the tablesassociated with the channels that are to be tuned are parsed. Theresults of the parsed tables are reported to the channel manager 1007 bythe data decoder 1010. Thereafter, based on the parsed results, thechannel manager 1007 updates the channel map 1008 and sets up a PID inthe demultiplexer 1003 for demultiplexing the tables associated with thedata service data from the enhanced data.

The system manager 1012 controls the booting of the receiving system byturning the power on or off. Then, the system manager 1012 stores ROMimages (including downloaded software images) in the first memory 1009.More specifically, the first memory 1009 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 1011 so as to provide the user with the dataservice. If the data service data are stored in the second memory 1011,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 1009 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory1009 upon the shipping of the receiving system, or be stored in thefirst 1009 after being downloaded. The application program for the dataservice (i.e., the data service providing application program) stored inthe first memory 1009 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 1013 operates thecorresponding application program stored in the first memory 1009 so asto process the requested data, thereby providing the user with therequested data service. And, in order to provide such data service, thedata broadcasting application manager 1013 supports the graphic userinterface (GUI). Herein, the data service may be provided in the form oftext (or short message service (SMS)), voice message, still image, andmoving image. The data broadcasting application manager 1013 may beprovided with a platform for executing the application program stored inthe first memory 1009. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 1013 executing the data serviceproviding application program stored in the first memory 1009, so as toprocess the data service data stored in the second memory 1011, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiving system that is not equipped with anelectronic map and/or a GPS system in the form of at least one of a text(or short message service (SMS)), a voice message, a graphic message, astill image, and a moving image. In this case, is a GPS module ismounted on the receiving system shown in FIG. 13, the GPS modulereceives satellite signals transmitted from a plurality of low earthorbit satellites and extracts the current position (or location)information (e.g., longitude, latitude, altitude), thereby outputtingthe extracted information to the data broadcasting application manager1013.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 1011, the first memory 1009, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 1013, the dataservice data stored in the second memory 1011 are read and inputted tothe data broadcasting application manager 1013. The data broadcastingapplication manager 1013 translates (or deciphers) the data service dataread from the second memory 1011, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 14 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiving system according to anotherembodiment of the present invention. Referring to FIG. 14, the digitalbroadcast receiving system includes a tuner 2001, a demodulating unit2002, a demultiplexer 2003, a first descrambler 2004, an audio decoder2005, a video decoder 2006, a second descrambler 2007, an authenticationunit 2008, a native TV application manager 2009, a channel manager 2010,a channel map 2011, a first memory 2012, a data decoder 2013, a secondmemory 2014, a system manager 2015, a data broadcasting applicationmanager 2016, a storage controller 2017, a third memory 2018, and atelecommunication module 2019. Herein, the third memory 2018 is a massstorage device, such as a hard disk drive (HDD) or a memory chip. Also,during the description of the digital broadcast (or television or DTV)receiving system shown in FIG. 14, the components that are identical tothose of the digital broadcast receiving system of FIG. 13 will beomitted for simplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descramble the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 2004 and 2007, and the authentication means will bereferred to as an authentication unit 2008. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.14 illustrates an example of the descramblers 2004 and 2007 and theauthentication unit 2008 being provided inside the receiving system,each of the descramblers 2004 and 2007 and the authentication unit 2008may also be separately provided in an internal or external module.Herein, the module may include a slot type, such as a SD or CF memory, amemory stick type, a USB type, and so on, and may be detachably fixed tothe receiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 2008, the scrambled broadcastingcontents are descrambled by the descramblers 2004 and 2007, therebybeing provided to the user. At this point, a variety of theauthentication method and descrambling method may be used herein.However, an agreement on each corresponding method should be madebetween the receiving system and the transmitting system. Hereinafter,the authentication and descrambling methods will now be described, andthe description of identical components or process steps will be omittedfor simplicity.

The receiving system including the authentication unit 2008 and thedescramblers 2004 and 2007 will now be described in detail. Thereceiving system receives the scrambled broadcasting contents throughthe tuner 2001 and the demodulating unit 2002. Then, the system manager2015 decides whether the received broadcasting contents have beenscrambled. Herein, the demodulating unit 2002 may be included as ademodulating means according to embodiments of the present invention asdescribed in FIG. 4 and FIG. 12. However, the present invention is notlimited to the examples given in the description set forth herein. Ifthe system manager 2015 decides that the received broadcasting contentshave been scrambled, then the system manager 2015 controls the system tooperate the authentication unit 2008. As described above, theauthentication unit 2008 performs an authentication process in order todecide whether the receiving system according to the present inventioncorresponds to a legitimate host entitled to receive the paidbroadcasting service. Herein, the authentication process may vary inaccordance with the authentication methods.

For example, the authentication unit 2008 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 2008 may extract the IP address from thedecapsulated IP datagram, thereby obtaining the receiving systeminformation that is mapped with the IP address. At this point, thereceiving system should be provided, in advance, with information (e.g.,a table format) that can map the IP address and the receiving systeminformation. Accordingly, the authentication unit 2008 performs theauthentication process by determining the conformity between the addressof the corresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 2008 determines that the two types ofinformation conform to one another, then the authentication unit 2008determines that the receiving system is entitled to receive thecorresponding broadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or anotherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with a receivingsystem-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 2008 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 2008determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 2008 determines that the information conform to eachother, then the authentication unit 2008 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 2008 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 2015 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 2015 transmits thepayment information to the remote transmitting system through thetelecommunication module 2019.

The authentication unit 2008 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 2008 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 2008 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 2008, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 2004 and 2007. Herein,the first and second descramblers 2004 and 2007 may be included in aninternal module or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 2004 and 2007, so as to perform the descrambling process.More specifically, the first and second descramblers 2004 and 2007 maybe included in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 2004 and 2007may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 2004 and 2007 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 2004 and 2007 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 2015, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 2012 of thereceiving system. Thereafter, the CAS software is operated in thereceiving system as an application program. According to an embodimentof the present invention, the CAS software is mounted on (or stored) ina middleware platform and, then executed. A Java middleware will begiven as an example of the middleware included in the present invention.Herein, the CAS software should at least include information requiredfor the authentication process and also information required for thedescrambling process.

Therefore, the authentication unit 2008 performs authenticationprocesses between the transmitting system and the receiving system andalso between the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 2008 compares the standardized serial numberincluded in the memory card with the unique information of the receivingsystem, thereby performing the authentication process between thereceiving system and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 2015, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 2012 upon the shipping of the presentinvention, or be downloaded to the first memory 2012 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 2016 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 2003, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 2004 and 2007. More specifically, theCAS software operating in the Java middleware platform first reads outthe unique (or serial) number of the receiving system from thecorresponding receiving system and compares it with the unique number ofthe receiving system transmitted through the EMM, thereby verifyingwhether the receiving system is entitled to receive the correspondingdata. Once the receiving entitlement of the receiving system isverified, the corresponding broadcasting service information transmittedto the ECM and the entitlement of receiving the correspondingbroadcasting service are used to verify whether the receiving system isentitled to receive the corresponding broadcasting service. Once thereceiving system is verified to be entitled to receive the correspondingbroadcasting service, the authentication key transmitted to the EMM isused to decode (or decipher) the encoded CW, which is transmitted to theECM, thereby transmitting the decoded CW to the descramblers 2004 and2007. Each of the descramblers 2004 and 2007 uses the CW to descramblethe broadcasting service.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiving system,as long as an external memory interface is provided, the presentinvention may embody a CAS system that can meet the requirements of alltypes of memory card that may be detachably fixed to the receivingsystem. Thus, the present invention may realize maximum performance ofthe receiving system with minimum fabrication cost, wherein thereceiving system may receive paid broadcasting contents such asbroadcast programs, thereby acknowledging and regarding the variety ofthe receiving system. Moreover, since only the minimum applicationprogram interface is required to be embodied in the embodiment of thepresent invention, the fabrication cost may be minimized, therebyeliminating the manufacturer's dependence on CAS manufacturers.Accordingly, fabrication costs of CAS equipments and management systemsmay also be minimized.

Meanwhile, the descramblers 2004 and 2007 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 2018, the received data may bedescrambled and then stored, or stored in the memory at the point ofbeing received and then descrambled later on prior to being played (orreproduced). Thereafter, in case scramble/descramble algorithms areprovided in the storage controller 2017, the storage controller 2017scrambles the data that are being received once again and then storesthe re-scrambled data to the third memory 2018.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 2019. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 2019 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 2019 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module2019. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1× EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 2019.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 2003 receives either the real-time data outputted from thedemodulating unit 2002 or the data read from the third memory 2018,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 2003 performs demultiplexing on theenhanced data packet. Similar process steps have already been describedearlier in the description of the present invention. Therefore, adetailed of the process of demultiplexing the enhanced data will beomitted for simplicity.

The first descrambler 2004 receives the demultiplexed signals from thedemultiplexer 2003 and then descrambles the received signals. At thispoint, the first descrambler 2004 may receive the authentication resultreceived from the authentication unit 2008 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 2005 and the video decoder 2006 receive the signalsdescrambled by the first descrambler 2004, which are then decoded andoutputted. Alternatively, if the first descrambler 2004 did not performthe descrambling process, then the audio decoder 2005 and the videodecoder 2006 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 2007 and processed accordingly.

As described above, the DTV receiving system and methods of processingDTV signals according to the present invention have the followingadvantages. More specifically, the DTV receiving system and method ofprocessing DTV signal according to the present invention is highlyprotected against (or resistant to) any error that may occur whentransmitting supplemental data through a channel. And, the presentinvention is also highly compatible to the conventional receivingsystem. Moreover, the present invention may also receive thesupplemental data without any error even in channels having severe ghosteffect and noise.

Additionally, by having the transmitting system periodically ornon-periodically transmit known data having a pattern pre-decided inaccordance with an agreement between the transmitting system and thereceiving system, and by having the receiving system use the known datafor performing carrier recovery and timing recovery, and forcompensating a phase change between repeating known data sequences, thereceiving performance of the receiving system may be enhanced in asituation undergoing severe and frequent channel changes. Furthermore,the present invention is even more effective when applied to mobile andportable receivers, which are also liable to a frequent change inchannel and which require protection (or resistance) against intensenoise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) transmitter for processing digitalbroadcast data, the DTV transmitter comprising: a signal generator forgenerating a first data group comprising first, second and thirdregions, the second region being positioned between the first and thirdregions, the first and third regions including main data, RS parity databut no enhanced data, the second region including enhanced data codedwith a first coding rate, enhanced data coded with a second coding ratethat is different from the first coding rate, a plurality of known datasequences, signaling information and RS parity data but no main data; aninterleaver for interleaving the first data group to generate a seconddata group, the second data group comprising fourth, fifth and sixthregions, the fifth region being positioned between the fourth and sixthregions, the fifth region including enhanced data encoded with one offirst and second coding rates, a plurality of known data sequences,signaling information, and RS parity data but no main data, the fourthregion including main data, RS parity data, and enhanced data, whereinenhanced data in at least one segment in the fourth region are codedwith the first coding rate and enhanced data in at least one segment inthe fourth region are coded with the second coding rate that isdifferent from the first coding rate; a trellis encoder for trellisencoding the second data group; and a modulator for modulating abroadcast signal including the trellis encoded second data group fordata transmission.
 2. A method of processing digital broadcast data in adigital television (DTV) transmitter, the method comprising: generatinga first data group comprising first, second and third regions, thesecond region being positioned between the first and third regions, thefirst and third regions including main data, RS parity data but noenhanced data, the second region including enhanced data coded with afirst coding rate, enhanced data coded with a second coding rate that isdifferent from the first coding rate, a plurality of known datasequences, signaling information and RS parity data but no main data;interleaving the first data group to generate a second data group, thesecond data group comprising fourth, fifth and sixth regions, the fifthregion being positioned between the fourth and sixth regions, the fifthregion including enhanced data encoded with one of first and secondcoding rates, a plurality of known data sequences, signalinginformation, and RS parity data but no main data, the fourth regionincluding main data, RS parity data, and enhanced data, wherein enhanceddata in at least one segment in the fourth region are coded with thefirst coding rate and enhanced data in at least one segment in thefourth region are coded with the second coding rate that is differentfrom the first coding rate; trellis encoding the second data group; andmodulating a broadcast signal including the trellis encoded second datagroup for data transmission.